Effect of the primary cooling rate on the motility and fertility of frozen-thawed rabbit spermatozoa

• Main Authors: Tatsuhiro Maeda, Enqi Liu, Kazutoshi Nishijima, Shinji Yamaguchi, Masatoshi Morimoto, Teruo Watanabe, Jianglin Fan, Shuji Kitajima
• Format: Article
• Language: English
• Published: Universitat Politècnica de València 2012-07-01
• Series: World Rabbit Science
• Subjects: cryopreservation; cooling rate; motility; spermatozoa
• Online Access: http://polipapers.upv.es/index.php/wrs/article/view/1080

<p>In the present study, we examined the effect of primary cooling rates on the motility and fertility of frozen-thawed rabbit spermatozoa. Rabbit semen diluted with an egg-yolk acetamide extender was cooled from room temperature to 5°C at four different rates (-0.1, -0.2, -0.4, -0.8°C/min) as a primary cooling step, then semen was frozen in liquid nitrogen vapour. After thawing, sperm cooled at -0.1°C/min showed the highest motility (40.7 ± 7.3%); there were no significant differences between the motilities of the -0.1, -0.2, and -0.4°C/min groups. The motility of frozen-thawed sperm cooled at -0.8°C/min (29.2 ± 6.8%) was significantly lower than that of sperm cooled at -0.1 and -0.2°C/min. The viability (-0.1°C/min, 38.1 ± 4.0%; -0.8°C/min, 24.3 ± 7.3%) of frozen-thawed sperm was closely related to its motility (-0.1°C/min, 36.7 ± 7.2%; -0.8°C/min, 22.3 ± 4.7%). Quality of post-thaw motile sperm cooled at different rates was estimated by comparing the fertilisation ability of the -0.1 and -0.8°C/min groups following artificial insemination. There were no significant differences in pregnancy rates and mean litter sizes. These data suggest that cooling rabbit semen at rates ranging from -0.1 to -0.8°C/min affects the viability but not the fertilisation capacity of motile spermatozoa after thawing.</p>